A novel lipolytic enzyme-encoding gene,lipO745, fromAspergillus oryzaeRIB40 was cloned and expressed inPichia pastoris. Purified recombinant LipO745 (rLipO745) had a molecular mass of approximately 60 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. rLipO745 exhibited maximum activity at 40 degrees C and pH 7.0 and was stable at temperatures <= 40 degrees C. The substrate specificity of purified rLipO745 was analyzed using alpha-naphthyl esters as artificial substrates and various triacylglycerol and sterol esters as natural substrates. From among a panel of alpha-naphthyl esters (C2-C16), alpha-naphthyl butyrate (C4), with an activity of 269 +/- 3.3 units/mg protein, was the optimal substrate for hydrolysis by the purified recombinant protein. TheK(m)andk(cat)values of rLiO745 for the C4 substrate were 0.073 +/- 0.0012 mM and 608 +/- 108 s(-1), respectively. The purified recombinant enzyme had considerable hydrolytic activity toward tributyrin, tripalmitin, and triolein, indicating lipase activity, and toward cholesteryl acetate, butyrate, palmitate, and oleate, indicating sterol esterase activity. Transesterification activities between tributyrin and cholesterol or between tributyrin and campesterol were also determined.